Production of oxytetracycline using streptomyces alboflavus (atcc 15388)

ABSTRACT

A fermentative process for the production of oxytetracycline which comprises fermenting a nutrient broth under aerobic conditions at a temperature between 22 DEG  and 30 DEG  C. by a mutant of Streptomyces alboflavus (Waksmann &amp; Curtis), and recovering accumulated oxytetracycline from the fermented broth.

United States Patent Villax [451 Jan. 25, 1972 [54] PRODUCTION OF OXYTETRACYCLINE [56] References Cited USING STREPTOMYCES ALBOFLAVUS UNITED STATES PATENTS (ATCC 15388) 7 2,516,080 7/1950 Sobin et al. ..195/80 X [72] Inventor: Ivan Villax, Lisbon, Portugal Y 1 s [73] Assignee: International Rectifier Corporation, Los FOREIGN PATENTS OR APPLICATIONS Angeles, Calif. 91,397 9/1959 Czechoslovakia ..195/80 [22] Filed: 1967 Primary Examiner-Joseph M. Golian [21] Appl. No.: 660,936 Attorney-Wenderoth, Lind & Ponack Related [1.8. Application Data [57] ABSTRACT Co i i -i p of 3613 A fermentative process for the production of oxytetracycline 1963, abandoned. which comprises fermenting a nutrient broth under aerobic conditions at a temperature between 22 and 30 C. by a mu- [30] Foreign Application Priority Data tant of Streptomyces alboflavus (Waksmann & Curtis), and Oct. 19, 1962 Portugal ..4o,140 Lim accumulaed ytwacydme the fermented [52] US. Cl ..195/80, 260/559 AT, 195/] 14 5 chims, No Drawings [51] Int. Cl. ..Cl2d 9/00 [58] Field of Search 195/80, 100, l14; 260/559,

PRODUCTION OF OXYTETRACY CLINE USING STREPTOMYCES ALBOFLAVUS (ATCC 15388) This application is in part a continuation of copending application, Ser. No. 312,877, filed Oct. 1, 1963 and now abandoned.

The present invention relates to the production of oxytetracycline and in particular to the production of oxytetracycline by means of submerged fermentation by a mutant strain of Streptomyces alboflavus. I

The referred mutant strain has been deposited in the collection of Central bureau Vor Schimmelcultures, Baarn, Holland, under the denomination streptomyces alboflavus M-l08-OX. (it is also on deposit at American Type Culture Collection as ATCC No. 15388.)

Streptomyces alboflavus is a known species and, according to Bergeys Manual of Determinative Bacteriology, 7th Edition, published by The Williams & Wilkins Company," Baltimore, Maryland, 1957, it was formerly described by Waksmann and Curtis in 1916 and reclassified b'y Waksman and Heinrici in 1948.

However, Streptomyces alboflavus, such as described and supplied by the various collections of strains, is not adequate for the production, either experimental or industrial, of oxytetracycline.

The original strain of Streptomyces alboflavus, which was submitted to mutation and selection with a view to obtaining the mutant utilized in the present process of invention, was obtained from the collection of Central bureau Voor Schimmelcultures, Baarn, Holland (hereafter referred to as CBS), and is a direct descendant of Waksmanns type strain. This strain produces essentially antibiotics belonging, with all probability, to the group of the actinomycines, showing R,s of 0.85 to 0.95, after the fermented broth has been submitted to paper chromatography, and a purple color under Wood light.

The mutant, object of the present invention, was obtained by ultraviolet irradiation of the single spore cultures of the above-mentioned original type culture followed by a careful selection according to known criteria and technique. Of the various mutants thus formed, several types were chosen, after analytical evaluation, for the production of oxytetracycline, one of which is hereinafter described in detail.

With a view, on one hand, to characterizing the mutant Streptomyces alboflavus Ml08-OX and, on the other, to demonstrating the amplitude of the changes of characteristics, following is the comparative description between:

Streptomyces albaflavus, obtained from CBS, Waksmann Type Strain.

Streptomyces alboflavus M-l 08-OX, a mutant obtained according to the invention from the previous strain, and

Streptomyces rimosus, (Sobin, Finlay et al.) a type strain obtained from CBS.

The latter was included in the present description solely for comparative purposes, as it is the best known micro-organism producing oxytetracycline. V

The three strains were simultaneously cultivated in 14 culture media and their characteristics, such as the color of culture and sporulation (in the case of such being present), color of formation of pigments, etc., were observed and described. After repeated cultures, the following characteristics, after 16 days of inculation at 26 C., were observed.

1. On coon steep liquor (0.6 percent) medium having the following composition:

Agar agar l grams Corn steep liquor 50% '3 grams Glucose l grams (NH,),HPO grams Kl-hPO, 7.5 grams MgSOfllLO I gram MnCl, 0.002 gram CuSO.-5H,O 0.002 gram ZnS0,-7H,0 0.025 gram Water 500 milliliters pH 7, after sterilization.

Streptomyces alboflavus, produces shiny, well separated, dirtyyellow colonies, no spores or pigment being formed, while Strepromyces alboflavus mutant M-l08-OX produces white to slightly greyish spore colonies and light brown diffusible pigment; Streptomyces riinosus grows scantly, without any sporulation, producing a beige colony with scant aerial mycelium and slight light brown diffusible pigment.

2. On corn steep liquor (0.4 percent) medium, of the same composition, as above, except for the quantity of corn steep liquor being 2 grams instead of 3 grams, the three strains grow similarly to that on medium No. 1, although the growth is slower.

3. On gelatin medium, having the formula:

Meat extract [.5 ,gram Peptone 2.5 grams Gelatin 80 grams Distilled water 500 milliliters pH 6.2, before sterilization.

rather slow liquefaction, Streptomyces alboflavus mutant I M-l08-4. Czapek-Dox-Dextrine medium of the formula:

Dextrine 5 grams NaNO; l gram KJIPO, 0.5 gram MgSO.-7H,0 0.25 gram KCl 0.25 gram FeSO 3 small crystal Agar agar 7.5 grams Distilled water 500 milliliters pH 6.8, after sterilization.

Streptomyces alboflavus produces well separated, round,

light beige colonies, which are surrounded by a white halo formed by young aerial mycelium with very scant, light beige diffusible pigment, while Streptomyces alboflavus mutant M-IOS-forming white aerial mycelium, which covers up the initial color. Streptomyces rimosus grows slowly without producing aerial mycelium and forming fused brown colonies and dark-beige diffusible pigment.

5. Potato plug:

A plug of potato (d) 1.5 cm., 3-6 cm. height) is washed with a solution of 10 percent Na CO and sterilized in an assay tube together with 1.5 cc. of distilled water.

Streptomyces albaflavus produces a pinkish-beige vegetative growth and scant dirty white to beige aerial mycelium, while Streptomyces albaflavus mutant M-l08-OX rapidly produces a thick white aerial mycelium showing a wrinkled aspect. Streptomyces rimosus grows well, covering the surface of the potato plug with a bronze to shiny bronze violet alveolated growth, without producing aerial mycelium. The color of the potato plug remains unchanged where there is no growth, with the exception of Streptomyces rimosus which produces a dark brown coloration of the plug.

6. Benett medium of the formula:

Yeast extract 0.5 gram Meat extract 0.5 gram l-lydrolyzed casein: l gram Glucose 5 grams Agar agar l0 grams Distilled water 500 milliliters 5 grams l2. Nutrient medium of the formula: Asparaglne 0.25 gram Mcatcxtract 1 gram K,HPO 0.25 gram Meat extract l.5 gram Agar agar 7.5 grams Peptone 2.5 gram Distilled water 500 milliliters 5 Agar agar 7.5 grams pH 6.9 after sterilization. Distilled water 500 milliliters pH 6.8, after sterilization.

Streptomyces alboflavus produces shiny, dirty white, distinct colonies without any aerial mycelium or pigment while .streptqmyces .alboflavus Produces l 'i streptomyces alboflavus mutant produces dark 10 dirty-white to slightly yellowish vegetative colonies with faint brown almost black colonies forming white aerial mycelium llght-yellow diffusible pigment, while Streptomyces albaflavus and bronze to bronze violet diffusible pigment. Streptomyces mutant Q l fi z'xys fi ggi ii gff z zg rimosus produces light yellow diffusible pigment, and light fft f i gf g. li g g I beige colonies with scant dirty-white aerial mycelium. am en I l e 'T l3. Glucose-Asparaglne medium of the formula: 8. Czapek-Dox medium of the formula:

Glucose 1 gram NaNO 3 1 gram Asparagine 025 gram K,HPO4 0.5 gram Meat extract 1 gram M souil o 0.25 gram leiiPo. 0.25 gram KCl 0.25 gram Agar agar 7.5 grams FcSO, a small crystal Distilled water 500 milliliters Distilled water 500 milliliters pH 6.9, after sterilization. Agar agar 7.5 grams PH On this medium the aspect of the three strains is similar to that of the previous medium, growth being slower and the There is no growth on this medium with the exception of a formed pigments lighten P llght'yellow Vegelat've growth the case of slmpto' l4. Sugar-Dextrine-Nitrate medium of the formula: myces alboflavus.

9. Emerson medium of the formula: Dextrine 5 grams NaNo 1 gram MgSO 7H,O 0.25 gram Yeast extract 2 grams KCl 025 gram Soluble starch 7.5 grams Dextrose l5 grams K HPo, 0.5 gram FcSO. a small crystal MgS0.-7H,0 0.25 gram Distilled water 500 milliliters Agar agar l0 grams pH 7. after sterilization. Distilled water 500 milliliters On this medium Streplomyces alboflavus produces rapidly growing white to beige aerial mycelium with light-yellow dif- On this medium Streptomyces alboflavus produces flat fusible P g strepwmyces albPflavus f" slightly wrinkled, yellow beige colonies and diffusible pigment P almost black vegetabtwe 'P will? dark brown of the same color, aerial mycelium is lacking, while Strepto 40 dlfi'uslble P g and Scam Willie aerial y pf myces alboflavus mutant M-l08-OX and Slreptomyces myces rzmosus produces vegetative growth and diffusible pi grimosus grow alike, producing yellow to beige vegetative coloh g a yellow browmsh colorant)", aerial nies and yellow brownish pigment, this being a bit lighter in mycellum being m the case f the last Strain The above-described media were prepared with products the firm E. MerckDarmstadt (inorganic comsupplied by Czapek DOX Starch ofthc formula pounds and asparagtne) and the remaining products by the firm Difco, Detroit. i a i 13? Streptomyces alboflavus mutant M-lO8-OX produces a 0 6 5 conidias in great number, contrarlly to its mother strain. The MgSO,-7H,) 025 gram chains of conidias often form open spirals. The conidias are el- KCI s lipsoidal, measuring 0.7 to 0.9 by LG and L5 microns, and i sfa V'gglg present a smooth surface. The masse spore color is olive buff. Distilled water 500 milliliters The Streptomyces alboflavus mutant M-l08-OX in the pH luficrsierilizmi m above comparative tests resembles in many aspects Streptomyces rimosus, but can be easily differentiated from Strepto- The three Strains grow exactly as they do on medium of myces rzmosus by the fact that one finds in the single spore culczapeknoxbexmnei tures of Streptomyces alboflavus mutant M-l08-OX, in an approximative proportion of l to 3,000 to l to 30,000, colonies Purple qg ccfmmerc'al medum of the firm showing the characteristics of the original mother strain, i.e., Dlfco' PH before 6O Streptomyces alboflavus (CBS), while no such colonies appear The three strains grow well and there is no change in the in single spore cultures of Streplomyces rimosus. pH. Further comparison is shown in the following:

TABLE S. alboflavus (Waksman et S. alboflavus M-108-OX, OBS NCIB 9453,.ATCC S. rimosua (Finlay et al.)

Curtis) Waksman CBS 16388 urface of spores by electron micro- Smooth Smooth Smooth.

scope.

Size and shape of spores 0.40.6,uxLO-l.4 rectangu- 0.7-0.9M .01.5u(0.40.7;4x .22 z in certain de- 0.6-0.7;lx0.8-1.4,l cylindrilaiisrod shaped (cylindriscendants) ellipsoidal to oblong ovoidal. cal. 03

Sporophnro inolpllol0gy Short, straight; chains of Straight to flexous with occasional hooks and Spirals; numerous.

spores rare, up to 12 spores pcr chain (usually loops; numerous sporophores; chain of spores up to 40 spores; synipodially branched on oat l to 6): monopodially meal agar.

branched on out nicnl near. W V H "A M Using l'lltllltllll e grouping belongs to. Ruins fleribi'll's Relinaculum apertum Spi'ra .ipi'ra (Pridhamfi,

tnlol' ul splllus "int nuls u Yellow (according to Pridhain) On calcium citrate agar: Pearl Pink Shell (3 ca) at edges, Lead Gray (5 iii) in center; on oat meal agar: Lead Gray (5 lb); on calcium rna- Belongs to series, white 3 late agar: olive-butt in center.

verticillata (Waksman). Ocher colored in center,

colonial but! at edge.

Table Continued S. alboflavus (Waksman at S. albo avua M-108-0X, CBS NCIB 9453,ATCC S. rimosus l i Curtis) Waksman CBS fl 15388 (Fm W et Pigment formation on Ettllngers tyro- None None Produces first hallochrome.

sine agar. which oxidizes into melanin.

Starch Hydrolyzed Hydrolyzed Hydrolyzed. Temperature of optimum growth, C 37 28 Calcium citrate agar, 6 g./l Not clarified Not clarified Clarified Cellulose Very good growth No growth. Utilization of carbon sources:

l-Rhamnosc Raffinosc I-nrabinose.

The data for S. alboflavus (Waksman et Curtis) Waksman and S. alboflavus M-l08-OX CBS are from parallelassays, unless otherwise indicated. All media of the composition as described in Waksman: The Actinomycetes, Vol. 11, Appendix 11, pages 328-334, The Williams Rt Wilkins Company Baltimore, Maryland, 1961.

The data for S. Rimasus (Finlay et al.) have been taken from:

1. Bergeys Manual of Determinative Bacteriology, 7th Edition, The Williams & Wilkins Company, Baltimore, Maryland, 1957, excepting results marked (x) which were obtained in parallel comparative assays with S. rimosur (Waksman et Curtis) Waksman CBS.

2. Prof. E. Baldacci, personal communication. 1

3. Pridham et al., Appl. Microbiol. 6, pages 52-79, 1958.

4. Waksman: The Actinomycetes, Vol. 1, page 59, The

Williams & Wilkins Company, Baltimore, 1959.

5. Ettlinger et al., Arch. fiir Mikrobiologie, 31, pages Zahssr; i hwrto fiir Mi l9$ 9 .1225 2 7. Color Harmony Manual, 4th Edition, 1958, Container Corp. of America, Chicago, Illinois.

No test made or data available.

Streptomyces alboflavus mutant M-108-OX is adequate for industrial submerged fermentation, giving high yields.

The aqueous nutrient medium for the industrial fermentation contains an assimilable nitrogen source, carbon source and mineral salts.

As a nitrogen source one can use caseine hydrolyzate, extract of malt, of barley or of com, com steep liquor, peanut meal, soya meal, etc.

As a carbon source one can use various carbohydrates containing glucose, dextrose, maltose, starch, dextrine, etc. Besides the mineral salts, present in traces, such as iron, copper, cobalt, zinc, the medium also contains calcium carbonate and ammonium phosphate with the primary regard to adjust the pH of the medium.

The quantity and proportion of the nutrient elements are indicated in the examples (infra).

The addition of N,N'-dibenzylethylenediamine (DBED) to the nutrient media, prepared according to the previous paragraphs, causes a higher yield in comparison to the similar parallel assays performed without addition of DBED. To obtain good results, the quantity of DBED to be added must be from 100 to 3,000 milligrams/liter of medium. Better results are obtained by adding DBED in the form of acetate or lactate in several fractions during fermentation, the initial quantity added to the medium before inoculation being 10 to 100 milliliters/liter. Fermentation is performed at a temperature of 24 to 30 C. with strong aeration in the order of 0.1 to 0.7 part of the volume to be fermented, varying according to the stage of fermentation.

To obtain best results the pH is adjusted to between 7 and 7.5 at the beginning of fennentation; then it decreases to 5.2-5.6 and afterwards returns to 6.2-6.5 at the end of fermentation.

III. Mutant amass; 6H Hat aerate; 13$ a itate; Soil.

under U.V. light from well sporulated S. alboflauus (Waksman ct Curtis) Waksman type strain, CBS.

proceeding in the following way:

One increases the pH of the filtrate of the acid extraction until pH 5-6 with aqueous ammonium (12 percent) and adds DBED acetate until a concentration of one-tenth up to onefifth in weight of the oxytetracycline contained in the fermented medium (the quantity of DBED already added during fermentation having been deducted in cases where it applies) is obtained. One then adjusts the pH to 8.5-9 with aqueous ammonium (12 percent) which causes the precipitation of the DBED complexes of oxytetracycline in an almost pure state, these having a composition equivalent to oxytetracycline DBED'Ca (in the event of the medium containing calcium ions). Complexes having another composition of lesser importance can also be formed. One filters the precipitate of the complex, washes it with water and dries it under vacuum at 35 to 60 C. After having pulverized the complex, one recrystallizes it in an aliphatic alcohol containing one to three atoms of carbon, and acidifies it until pH 1 to 2 with gaseous hydrochloric acid. The oxytetracycline hydrochloride thus formed crystallizes after 6 hours.

By acidifying the complex up to the isoelectric point in aqueous medium, the oxytetracycline precipitates in the form of base, having the formula:

22 24 2 9' 2 and the following centesimal composition:

Calculated: C 53.22% H 5.68%; N 5.64%; H O 7.26%

Found: C 53.16% H 5.61%; N 5.7%; H 0 7.4%

The melting point is l-183 C. with decomposition and the optical rotation [ah-196.5 (C=l in l/lO N HCl). Ultra violet absorption in 0.1 molar phosphate-buffer at pH 4.5 lfin; a .298, a-.92; t2J6.J..ma-.QOQate it- Regardless of whether the product obtained is hydrochloride or base, by comparison with the corresponding standards of reference (of the Food and Drug Administration) it is identical to oxytetracycline from the standpoint of both analytical and antibacterial action. The industrial advantage of the present process of invention, using the artificial mutant Streptamyces alboflavus M-l 08-OX, consists essentially in the very high yields obtained, which surpass be far the highest yields already published when using strains of Streptomyces rimosus.

The following examples are used to illustrate the present process of invention.

EXAMPLE 1 (This exemplifies mutant production). Streptamyces alboflavus (typestrain CBS) is first transferred to two culture media (1 and 2 infra), conveniently in large (22/180 mm.) test tubes (at least six tubes each) with a view to obtaining sporulation. The composition of media 1 and 2 is as follows: 1. Mutation: Medium No. 1

Eight hundred milliliters of tap water are heated to boiling, 60 grams of oat flakes are added slowly and then digested on the water bath of 15 minutes. The digested mass is then filtered, while still hot, through a gauze sheet, 20 grams of agar added to the filtrate and the mixture heated until homogeneous admixture of the agar is achieved, after which the whole is made up to a volume of 1,000 milliliters with tap water. The pH is then adjusted to 6.3 and the mass subjected to sterilization in an autoclave at 120 C. for 20 minutes. The resultant oat flakes extract solution has a pH of 6.8 after the sterilization.

Medium No. 2

Agar 20 grams Calcium citrate grams Ammonium chloride 0.5 gram Dipotassium hydrogen phosphate 05 gram Glycerin grams Tap water 1,000 milliliters After adjusting the pH to 6.9, sterilization is effected at 120 C. for 30 minutes. Final pH 6.7.

Ripe spores are usually obtained after 2 to 4 weeks when incubating at 27-28 C.; if not, subcultures are made, alternating the above two media, until sporulation occurs.

Afterwards, the best sporulated tube is selected, and 5 milliliters of sterile water added to it and the tube shaken with a view to obtaining a good spore suspension.

This spore suspension is then diluted 1,000, 10,000 and 100,000 times with 0.5 percent aqueous agar and maintained at 40-45 C.

From 45 Petri dishes (100 mm.), previously prepared, containing about 25 milliliters of medium l, are inoculated with i k-2 milliliters of the above agar spore suspension diluted to 1,000, 15 with the 10,000 dilution and the remaining 15 with the 100,000 dilution, in a sterile incubation box having a 60 watt ultraviolet sterilization lamp (Philips or equivalent) near the top and 40 to 65 centimeters from the bottom.

The unique mutagenic treatments are the heat in the 0.5 percent spore suspension and the U.V. light efiect during dilution and pouring out same on the plates (which is made at the usual rate without exposing the plates or spores to the U.V. rays for too long).

The plates are then incubated at 27-28 C., preferably in a cardboard box so as to avoid light.

The screening for mutants is made at the 6th, 9th and 12th day of incubation for colonies of dark brownish pigmentation and strong fluorescence halo under Wood light, etc. The colonies are marked with glass writing pencil under the plate and incubated for 3 to 4 weeks more until the spores are ripe and well developed.

The marked colonies are cut out under sterile conditions and U.V. light, placed in a sterile test tube, containing three to four small glass balls and 3 milliliters of water, and then strongly shaken for minutes.

Test tubes containing media 1 and 2 (six of each) are then inoculated with the so-obtained spores suspension and the remaining amount is used for qualitative and quantitative evaluation of oxytetracycline production. The selected mutants kept on agar slants are submitted subsequently to further mutations by repeating the above mutation technique until substantial oxytetracycline is produced by one of the mutants, 11. Evaluation of oxytetracycline production:

One inoculates simultaneously, with 2 to 3 drops of the above spore suspension of each mutation type, two 200 milliliter Erlenmeyer flasks, containing 30 milliliters of the following medium:

Medium No. 3

Corn steep liquor 10 grams CaCO 1 gram (NH.),HPO, 2 grams Dextrose 10 grams MgSO. 0.25 gram Tap water 1,000 milliliters One adjusts the pH to 6.6 and sterilizes for 30 minutes at C. (final pH 6.4 to 6.3).

The inoculated flasks are shaken for 24 hours at 27 to 28 C. (in a rotatory or reciprocating shaker).

Afterwards, I milliliter of each flask is transferred to a 200 milliliter Erlenmeyer flask, containing 30 milliliters of the following medium:

Medium No. 4

Corn steep liquor (50%) 30 grams CaCO, 9.5 grams (NH|)1S0| 2.6 grams Dextrose grams Tap water 1,000 milliliters The pH is adjusted to 6.2 and sterilization effected for 30 minutes at 120 C.

Incubation is then carried out for 24 hours at 27-28 C. in a shaker.

After 24 hours of incubation, l milliliter of each flask is transferred to 300 milliliters Erlenmeyer flasks, containing 40 milliliters of the following medium:

Medium No. 5

Corn steep liquor (50%) 25 grams Corn starch (semihydrolyzed. viscous) 55 grams CaCO, 8 grams M 5.7 grams NH,Cl 2 grams ZnSO, 0.05 gram CoC1,*6H,O 0,002 gram MnSO -4H, O 0.05 gram FeSO 0.0l gram Tap water 1 liter To each flask, containing 40 milliliters of this medium, is then added 1 milliliter of a mixture (prepared under heating) of 14 parts by weight of lard and 2 parts by weight of peanut oil and sterilized for 30 minutes at 120 C. The flasks are then shaken for a week at 28 C.

The fermented broths are acidified with dilute hydrochloric acid to pH 1.5 and shaken in a reciprocating filter for 30 minutes. After filtration, the filtrates are paper chromatographed in conventional manner, using oxytetracycline-HCI as standard. The oxytetracycline-producing strains are submitted once again to the same mutation and selection process as described above, and the others discarded.

During this second treatment, there are selected 30 to 40 colonies which are evaluated after shake flask fermentation by a standard oxytetracycline assays method and the highest oxytetracycline yielding strains used for industrial production. A representative mutant obtained by this method is the aforesaid S. alboflavus mutant M108-OX (ATCC 15338-NC1B 9453).

In case the yields do not attain values over 6 grams, a third repetition of the process on the selected mutants is performed. By such repeated selections, mutants producing 10 grams/liter of oxytetracycline can be obtained.

For further description of methods for the qualitative and quantitative determination of oxytetracycline in the fermented flasks, see Novelli et al., 1960, Sulla determiniazione quantitativa dei prodotti tetraciclinici mediante cromatografia radiale." Farmaco (Pavia), Ed. Prat. 15: 483-492.; for chromatography using oxytetracycline-HCI as standard and for quantitative determination use spectrophotometric determination as described in U.S.P. XV.

EXAMPLE 2 (Examples 2 to 5 inclusive exemplify fermentation by mutants obtained as precedingly described.)

All media in this and the following examples are prepared with tap water.

One liter of the sterilized medium having the compositions:

Corn steep liquor l grams Sugar grams CaCO; l gram (NH,),HPO 2 grams KH.,PO, 2 grams MgSO,7H,O 0.25 gram Water l,000 milliliters is inoculated with 1 ml. (milliliter) of a spore suspension of Strepromyces alboflavus mutant Ml08-OX and incubated at 25 C. in a rotatory shaker of 36 hours. Afterwards, a pilot fermenter containing a sterilized medium of the composition:

is inoculated with the above mentioned 36 hours preculture.

Submerged fermentation is then performed at 26 C. under stirring and sterile aeration.

The pH of the medium and the quantity of oxytetracycline formed are determined at several intervals, giving the following values:

Period of fermentation Amount of oxytetracycline hours pH meg/ml.

0 7.2 36 6.2 180 46 5.9 1200 62 5.7 1l00 85 5.3 3400 l 10 5.6 4900 I35 6.3 6000 150 6.35 6600 micrograms per milliliter Fermentation is stopped after I50 hours, showing a final concentration of oxytetracycline of 6.6 grams per liter.

EXAMPLE 3 The procedure according to example 2 is repeated, but N,N'-dibenzylethylenediamine diacetate is added to the medium in several fractions: 8.4 grams before inoculation, 8.4 grams after 50 hours of fermentation and 8.4 grams after 120 hours. The amount of oxytetracycline obtained after 140 hours is 8.1 grams/liter of broth.

EXAMPLE 4 The fermented broth, obtained in example 2, is acidified with sulfuric acid (25 percent) until pH 1.5, filtered, and the mycelium washed with water. The combined filtrates have a volume of 240 liters. 2 grams/liter of ethylenediaminetetraacetate sodium (sequestering agent) are then added. The pH is adjusted to 6 with aqueous ammonia (12 percent), 150 grams of N,N-dibenzylethylenediamine diacetate added and the pH raised to 9.5 with aqueous ammonia (l2 percent). After stirring for 3 hours, the formed precipitate is filtered and washed until the pH of the washing waters reaches pH 7. The precipitate is dried at 50 C. under vacuum. The dry precipitate obtained is ground and then suspended in twice its weight of methanol. After stirring for 30 minutes, it is acidified with gaseous hydrochloric acid to pH 2 and then with hydrochloric acid (36 percent), the pH lowered to 1.5 and the whole stirred. The mass is filtered, washed with methanol and dried under reduced pressure for 6 hours. Yield in hydrochloride of oxytetracycline: 8] percent.

EXAMPLE 5 The product obtained in example 4 is suspended in the equal weight of methanol and its pH is adjusted to 7.8 with a mixture of 1:1 methanol and triethylamine. The solution thus obtained is filtered. Then the pH is adjusted to 5 and water added in the proportion of five times the volume of the solution. The oxytetracycline base crystallizes. After filtering it off, it is dried under reduced pressure and the base obtained in a yield of 92 percent.

What is claimed is:

1. A fermentative process for the production of oxytetracycline which comprises fermenting a nutrient broth under aerobic conditions at a temperature between 22 and 30 C. by Streptomyces alboflavus (ATCC 15388), and recovering accumulated oxytetracycline fromthe fermented broth.

2. A process according to claim 1, wherein the fermentation is submerged and the nutrient medium contains assimilable carbon and nitrogen sources and mineral salts.

4. A process according to claim 3, wherein the nutrient medium contains calcium ions and the oxytetracycline is recovered in the form of N,N '-dibenzylethylenediamine-calcium complex.

5. A process according to claim 1, wherein N,N- dibenzylethylenediamine diacetate is added portionwise to the nutrient broth during the fermentation, the amount added being from about to about 3,000 milligrams/liter of medium. 

2. A process according to claim 1, wherein the fermentation is submerged and the nutrient medium contains assimilable carbon and nitrogen sources and mineral salts.
 3. A process according to claim 1, wherein the fermented broth is acidified to a pH of 1 to 2 with an acid, the resultant medium is filtered, the pH of the filtrate is increased with aqueous ammonium to pH 5 to 6, N'', N''-dibenzylethylenediamine diacetate is added to a total concentration of from about one-tenth up to about one-fifth by weight of the oxytetracycline in the medium, the pH of the medium is adjusted to 8.5 to 9 with aqueous ammonium, and the oxytetracycline is recovered in the form of N, N''-dibenzylethylenediamine complex.
 4. A process according to claim 3, wherein the nutrient medium contains calcium ions and the oxytetracycline is recovered in the form of N,N''-dibenzylethylenediamine-calcium complex.
 5. A process according to claim 1, wherein N,N''-dibenzylethylenediamine diacetate is added portionwise to the nutrient broth during the fermentation, the amount added being from about 100 to about 3,000 milligrams/liter of medium. 